If you read our story on the pre-release drivers, then you'll know what to expect: compatibility with Radeon HD 7900- and 7700-series graphics cards in Windows 7 and Vista, support for super-sampling antialiasing on those same cards, and Eyefinity 2.1 enhancements, which include the option to set custom resolutions, resize and move the taskbar, and dynamically switch between different profiles. If you're curious, the release notes have a more detailed list of the changes.

By the way, these drivers don't support the freshly announced (and soon-to-be-released) Radeon HD 7800 series. Radeon HD 7850 and 7870 graphics cards are due out on the 19th, and AMD will presumably have a new pre-release driver out then.